Now she’s singing for a considerably large audience, but she’s always trying to recapture that feeling of effortless joy.

“We have to be free, like a bird has to feel free inside to be able to sing,” she said. She can’t be too worried about making a mistake, or pleasing everyone, or feeling the weight of the production resting on her shoulders.

“You have to have this freedom in your soul so you feel free to create,” she said. “Otherwise, you can’t create. If you feel like in a prison — like, ‘Oh my God, I depend on these people. If I can’t do it, this is the end’ — you can’t do it.

“You have always to feel like I will do my best. I will have fun with it. I will enjoy it so much and I will give my heart. Even if something is not so perfect, I will give my heart. I will put it inside of this.”

Maybe that’s what Campbell heard: Krasteva putting her heart into her role, no matter how small. He’s counting on her to do the same with “Delilah.”

Singing Lessons

If you really want to hear “The Voice,” don’t bother watching TV. It’s opera season, and the San Diego Opera is bringing in more than a dozen singers whose pipes will blow away anything you’ve seen on the tube.

This year, we’re going to focus on four of them, representing each voice type (soprano, mezzo-soprano/alto, tenor and bass), and talk to them about their craft.